1. Field of the Invention
Disclosed exemplary embodiments are directed to a heat transfer evaluating apparatus for a nano-fluid, and more specifically, to an apparatus that may determine the utility of a nano-fluid having a heat transfer improvement effect by measuring a convective heat transfer coefficient of the nano-fluid under flow conditions of the nano-fluid.
2. Description of the Related Art
Nano-fluids refer to colloidal compound fluids whose heat transfer capacity has been improved by adding a tiny amount of nano-size solid particles, whose thermal conductivity is significantly high, to a fundamental heat transfer fluid such as water, ethylene glycol, etc. to raise the thermal conductivity, thus improving the overall heat transfer capacity. Recently, a study has been intensively conducted domestically and internationally with respect to production, thermal property measurement, natural and forced convective heat transfer and boiling heat transfer of the nano-fluids.
In determining the heat capacity of nano-fluids, it has been primarily determined by measuring the thermal conductivity of the nano-fluids in the static state whether to be able to improve the heat transfer capacity of the nano-fluids. However, the addition of the nano-particles to the fundamental heat transfer fluid is generally accompanied with increase in viscosity as well as improvement of thermal conductivity. If the thermal conductivity of the nano-fluids has been improved but more pump force is required to drive the fluids, it needs to be determined whether to use the nano-fluids by calculating the whole expenses taking into consideration the heat transfer and necessary dynamic force. Accordingly, an experiment for convective heat transfer is required to make final determination on the heat capacity of samples of the nano-fluids.
A duplicate-pipe heat exchanger or an internal flowing apparatus using a heated pipe may be considered as a typical convective heat transfer coefficient experiment apparatus. However, such an experiment apparatus is complicated and large in volume because of even including peripherals such as a constant-temperature tub and a pump. Accordingly, there exist diverse difficulties in evaluating the convective heat transfer capacity of the nano-fluids.
And, the convective heat transfer experiment requires more expenses and time in contrast to the thermal conductivity measurement that is executed in the static state, and has a problem that many errors may be sometimes involved in the convective heat transfer coefficient calculated finally.
For instance, there could be considered problems such as time and expenses required to secure such a sufficient amount of nano-fluid samples to fill the inside of the apparatus, difficulties in washing the inside of the apparatus when the samples are exchanged, a long time taken to make the apparatus reach the steady state, and increase in uncertainty that could be involved in the convective heat transfer coefficient when the accuracy of the acquired data and thermal losses caused during the measurement process are not exactly calculated.
There is a need of providing a new apparatus different from existing apparatuses in terms of expenses and environmental problems caused when the samples are disposed.